Calcium magnesium acetate (CMA) is useful for deicing and several methods for making CMA-containing deicing compositions are known. In the context of this invention, the term CMA will mean calcium magnesium acetate-containing compositions, including pure compositions or mixtures containing crystalline and/or amorphous, hydrated and/or dehydrated calcium magnesium acetate, and/or calcium magnesium acetate double salt. Crystalline and/or amorphous magnesium acetate and/or calcium acetate may also be present. The CMA may also contain small amounts of calcium and/or magnesium hydroxides or oxides as impurities. The term CMAK includes the materials defined as components of CMA, and in addition, potassium acetate.
Commonly assigned U.S. Pat. No. 4,885,071 discloses a process utilizing a pumpable slurry which forms substantial quantities of a 1:2 calcium:magnesium ratio CMA double salt. As used herein the ratio describing a CMA or CMAK product will be the molar ratio of calcium to magnesium in the product. The slurry process disclosed therein includes preparation of both alkali and alkaline earth metal acetates.
Several related patents to Gancy, U.S. Pat. Nos. 4,426,308, 4,377,488 and 4,444,672, disclose the use of 2-5% of alkali metal hydroxides in addition to calcium magnesium acetate (CMA). In these patents, it is generally taught to add excess acid to the alkali earth bases and thereafter to add 2-5% (weight) of alkali metal hydroxide (potassium hydroxide is disclosed) at the end of the neutralization step to neutralize excess acid. In U.S. Pat. No. 4,400,285 there is disclosed the combination of calcium oxide with potassium acetate in which potassium acetate is described as a soluble agent which is also a deicer.
In none of the above-described patents is it disclosed that there is a synergy between potassium acetate with CMA to improve the performance of calcium magnesium acetate as a deicing agent.
We have now discovered, surprisingly, that a solid mixture of CMA and potassium acetate (CMAK) either in crystalline form or as an amorphous combination of salts, has unexpectedly superior deicing properties compared to those of calcium magnesium acetate (amorphous, crystalline and/or double salt), calcium acetate or magnesium acetate. The superior properties of CMAK include, but are not limited to, improved deicing characteristics sustained constantly over the useful subfreezing temperature range of about 15.degree. F. to about freezing (32.degree. F.). There is also a persistent improvement in deicing properties of CMAK without drop off at any given subfreezing temperature, for at least one hour after application to ice.
It is thus an object of the present invention to provide an improved deicing composition comprising acetates of calcium, magnesium and potassium (CMAK) in which the potassium acetate is present in an amount relative to the calcium acetate and magnesium acetate to provide improved ice melting properties, as compared to the same weight of calcium magnesium acetate, which improvement remains relatively constant over the useful subfreezing temperature range of about 15.degree. to about freezing (32.degree. F.), and which improvement in deicing performance is persistent without drop off at a given subfreezing temperature for at least about one hour after application to ice.